This invention relates to means for and to a method of reducing mechanical vibration and acoustical noise between the dynamoelectric machine and its application. More specifically, the particular application shown and described in the instant disclosure relates to mounting an electric motor on the transmission case of a washing machine for effectively damping mechanical vibration and acoustical noise transmitted therebetween.
Generally, in many applications, such as in a washing machine, it is highly desirable to minimize the amount of mechanical vibration and noise emitted by the appliance during operation thereof. In an effort to damp the transmission of mechanical vibration and noise, it has long been conventional practice to interpose an elastomeric grommet or pad between an electric motor and its application. In many instances, the rubber grommet was fitted into an aperture provided in the application frame and a bolt or fastener, approximately the same diameter as a central bore extending through the grommet was utilized to fasten the application to the motor. When a nut was threaded on the stud so as to at least partially compress the grommet, the grommet bore expanded radially inwardly and thus made good contact with the stud extending through the grommet bore. This typical prior art construction is shown in FIG. 6 of the drawing figures. While this prior art system of noise and vibration reduction did, in fact, significantly reduce the transmission of noise and mechanical vibration between the application and the motor, significant noise and vibration levels, as measured by mechanical accelerometers (expressed in milli-G's) and acoustical sound measuring apparatus (expressed in sones) was still appreciable. Moreover, over time, these prior art elastomeric grommets tended to become more stiff, thus transmitting even more mechanical noise and vibration.
Thus, there has been a long-standing need to even more effectively reduce the transmission of acoustical noise and mechanical vibration between a motor (e.g., a dynamoelectric machine) and its application in a simple and cost effective manner which may be readily installed both during manufacture of the appliance and during field service thereof.